+ 
2,000 
BIRDS COUNTED PER DAY 
8 
CENTRAL 
@ 
\/ EGG LAYING 
*% 
e Span of dates \ 
MAR APR MAY JUN JUL 
io 20 30 2) 
10 20 
MAR APR MAY JUN JUL 
Fig. 4.—Egg-laying and migration seasons of the tree swallow in different 
areas of the state (see Fig. 1). Spring and fall 
lines (1967-1970) show the highest daily count of each 2 days (left scale) . Asterisk symbols represent counts made in other 
or by other observers. Shaded areas show the pe 
during which egg laying has been recorded. Dot s 
represent the eastern side. 
rcent of eggs laid on a given date (right scale, 
ymbols represent counts made on the western si 
North only) or the span of 
de of the state; lines withou' 
Derrent of enas laid 
